C. armatum is also known as the African rainbow crab, or (in German) Harlequin crab. In case you may ask: they do come in those pretty and intense colours
This cute little guy volunteers as one of my test animals for EMG studies on Crustacean leg muscles. I also tried working with Pseudosesarma moeshi, Eriocheir sinensis, Carcinus maenas and Cancer pagurus. Most of them are quite some assholes and for the sake of my fingers I stuck to these colourful small guys. Unfortunately a few months ago the EU changed the Animal Welfare Act which now leads to stricter regulations. Crabs are now seen as on the same 'level' as mice when it comes to narcosis and stress-levels. That's a nightmare for scientists who now spend almost more time writing applications instead of doing actual research. Ain't it funny how these rules are always made by people who don't know a thing about systematics and neurobiology?